For future high-speed optical networks, there is a strong demand for realizing an all-optical wavelength conversion (WC) operation without the necessity of multiple optical-electronic-optical (O-E-O) transponders and that enhances network properties like reconfigurability, non-blocking capability and wavelength reuse. Several methods for all-optical WC have been proposed based on self-phase modulation (SPM), cross-phase modulation (XPM), and cross-gain modulation (XGM). However, four-wave mixing (FWM) is one of the most promising schemes to achieve wavelength conversion, because it is fully transparent to the signal bit rate and modulation format. FWM based wavelength conversion can be accomplished in the semiconductor optical amplifier (SOA) or optical fiber, however, the transmission speed in the SOA is limited due to the response time of the carriers.
High speed all-optical WC can be realized by using single pump and multi-pumps in a nonlinear fiber, specially, high-nonlinear fiber (HNLF). In single pump scheme, the conversion is usually polarization sensitive, and the converted spectrum is inverted relative to that of the original signal. Recently, the coherent detection has been proposed to be a promising way to increase the spectral efficiency and to compensate for optical transmission impairments in the electrical domain. With digital coherent detection, PolMux-RZ-QPSK is shown to be a promising modulation format for 100-Gb/s high-speed transmissions due to its high spectral efficiency as well its tolerance toward chromatic dispersion (CD) and polarization-mode dispersion (PMD). Additionally, comparison to binary modulation formats, the spectral efficiency of octaphase shift keying (8-PSK) can be increased 6-fold with polarization multiplexing, and it is more feasible for the applications of digital signal processing because of the reduce baud rate. However, no wavelength conversion has been demonstrated for any polarization multiplexing signal.
Accordingly, there is a need for an all-optical wavelength conversion for a polarization multiplexing optical signal